High-frequency tuning coil



1947- P. D. ZOTTU HIGH FREQUENCY TUNING COIL Filed May 2, 1944 2 Sheets-Sheet 1 mmvma PAUL D ZOTTU. (14 E Aug. 12, 1947. zo u 2,425,411

HIGH FREQUENCY TUNING COIL Filed May 2, 1944 2 Sheets-Sheet 2 IN VEN TOR.

PAUL D. ZOTTU A'Horneng.

Patented Aug. 12, 1947 HIGH-FREQUENCY TUNING COIL Paul D. Zottu, Indian Hills, Ky., assignor to The Girdler Corporation, Louisville, Ky., a corporation of Delaware Application May 2, 1944, Serial No. 533,798

This invention relates to variable inductance devices such as high frequency tuning coils and has for an object the provision of a coil of high electrical efliciency of rugged, reliable, mechanical design and adustable in its electrical properties over a wide range.

Heretofore, helical tuning coils have been proposed in which the turns of the coil have served as threads in order to advance bridging arms or contacting devices lengthwise of the coil. The mounting of these bridging members or contactors has presented considerable difliculty because they must not only be free for axial movement but they must also have freedom of movement in other directions. Besides relatively free movement in a number of directions, good electrical contact ,must be maintained at all times. This is important from the standpoint of preventing undue heating. If poor contacts are present, arcing and burning effects may appear which may seriously injure the conductors and prevent subsequent adjusting or tuning operation of the coil.

In carrying out the present invention in one form thereof, a helical coil is mounted from suitable insulating supports with an elongated conductor supported coaxially thereof, The elongated conductor forms a drive shaft along which a pair of arms are slidably and rotatably mounted. These arms are carried by a sliding member which has a plurality of resilient fingers to insure intimate electrical contact with the elongated conductor. These fingers also permit a certain flexibility or relative movement of the slidable member with respect to the elongated conductor or drive shaft. In accordance with the invention, no torque is directly applied to the sliding member. The arms are rotated by means of driving members mounted on the elongated conductor at the respective ends of the tuning coil and between which there extends a pair of driving rods. These rods engage rollers carried by the respective arms and serve to drive the arms and the sliding member circumferentially and axially of the coil in one direction or the other.

For a more detailed description of the invention and for further advantages thereof, reference is now to be had to the accompanying drawings in which:

Fig. l is a perspective view of a tuning coil embodying the invention;

Fig. 1a is an enlarged sectional view ,of a supporting bolt and gradient electrode;

Fig. 2 is a view partly in section taken through the center of the arms and normally of the turns of the coil;

'7 Claims. (Cl. 171242) Fig. 3 is a fractional side view of the upper end of the arm of Fig. 3., and

Fig. 4 is a detail view of resilient contact fingers carried by the slider,

Referring to the perspective view of Fig. 1, the tuning coil 10 is helical in form and is construct.. ed of relatively heavy tubing, preferably of copper or other suitable conductor. The coil is supported from a base I l which may be of hardwood. The turns of the coil are mechanically interlocked by means of three electrical insulating members l2, l3 and II of identical construction. Each member may be of hardwood or any other suitable insulating material. Referring particularly to the members I! and I3, each such member is drilled to receivebolts I! carried by the respective turns of the coil. For example, each bolt or supporting member, Fig. 1a, is provided with a base Isa which is soldered, welded or brazed to the outer surface of the respective turns of the coil l0. Each bolt. carries a spacer l5b above which is mounted a gradient or voltage distributing ring 150, of generally rectangular shape. Though each turn is electrically insulated from the other turn, each turn is mechanically interlocked with the remaining turns of the coil by means of the bolts l5, and the insulating members l2|l.

The coil I0 is supported in spaced relation with the base II by means of brackets l6 carried by the insulators l'i. Extending coaxially through the coil is an elongated tubular conductor 20 of fairly large diameter. It is iournalled at 2| and 22, each journal or hearing being supported by the insulators 23 which are in turn carried by superstructure 24 mounted from the base I I. On one end of the conductor or drive shaft 20 there is mounted a pulley 25 which carries a belt 26. This belt extends to a pulley 21 driven by a motor 28 through suitable reduction gearing 29, The motor may be remotely controlled through a cir-= cuit including the conductor 30. By means of insulators 3|, a disc 32 may be utilized to drive a flexible cable 33 which extends to the transmitter 34v of a remote position indicator. The details of this indicator need not be disclosed since any of the well known systems may be utilized to indicate at a receiver location the position of cross arms 35 and 36 which are secured to and extend from a slider or slidable member 31 carried on the conductor 20.

The arms 35 and 38 are driven by means of a pair of driving arms 38 and 39, of insulating material, mounted on conductor 20 outwardly of and in spaced relation-with the respective ends of the coil It. The outer ends or the arms II and 88 are interconnected by means of driving rods 40 and ll. From brackets carried on opposite sides or the arms 38 and II, rollers a are mounted to engage the rods 40 and II on opposite sides thereof. Only one of these brackets. Figs. 1, 2 and 3, th bracket 42, is shown. They are both of identical construction.

By energizing the motor 28 so as to drive the shaft 20 in a clockwise direction, as viewed from the left in Fig. 1, the arms I! and l! will be moved to the right of the helical coil l0. as viewed in Fig. 1. This movement is insured by reason of resilient contact heads or members II and ll carried by the respective ends of arms SI and 38. These resilient contact members wipingiy engage and partly encircle the conductor of coil l0. Hence, upon rotation of arms I! and ll. the turns of the coil l act as a propelling means or thread and cause the arms 35 and 3| and the slidable member 31 to move longitudinally of the coil. The arm 35 from the slidable member 31 to the resilient contact head 44 may be of insulation, whereas the arm 38 may be of copper or other good conductor. Hence, an electrical circuit may be completed from a fitting 50 electrically connected to one end of the conductor 20, this circuit extending along the conductor 20, through the slidable member 31, the conducting arm 38, the contact head 4!, and to one turn of the coil. The circuit includes all oi the turns to the right of the position of the arm 86. The external circuit is completed from the other end of the coil (not shown) The coil may also be utilized by completing the electrical connection at the free end of the coil shown in Fig. 1. The circuit would then be by way of the conductor 20, the arm 36 and thence to the turns of the coil located to the left or arm 36. If the conductor connected to the lefthand end of the coil in were to extend parallel to the central conductor 20, there would be introduced in the circuit inductance due to the loop formed thereby.

By means of the previously described connections, this result is avoided, and when the arm 36 is driven to its rightmost position with respect to coil Iii as viewed in Fig. 1, the circuit enters at 50 and from the arm SI goes directly to the end of the coil and outwardly therefrom. There is not present the loop which would introduce undesired inductance into the circuit.

The coil I0 is preferably cooled by the circulation of a suitable fluid therethrough, such as water. If desired, either or both the incoming and outgoing conductors may be cooled. When the incoming conductor is cooled, it will be attached to the fitting ll. Thus, the fitting 50 serves both as an electrical and fluid or pipe connection. Water introduced through the incoming conductor (not shown) flows through the coupling 50 and thence through a rubber hose 53. The conductor III is blocked against fluid flow. To provide the required insulation, the insulating or rubber hose 53 may be coiled around a suitable support as indicated at H. The opposite end of the coil of rubber hose extends, as indicated at 55, to the lefthand end of coil Ill. The cooling fluid then traverses the coil and exit through the opposite end of the coil and by way of the outgoing conductor (not shown) connected thereto. Due to the size oi. conductor III it need not, though of course it could, be cooled. Normally it remains at a satis- 76 4 factory temperature due to radiation or conductive transfer of heat to the atmosphere.

From the foregoing description, it will be seen that as the slidable member 31 and the arms 35 and I8 rotate they move axially of the conductor 20. Because of this double movement, any irregularities in the manufacture of the coil l0 are likely to introduce considerable friction and possible binding of the parts. Though the turns are mechanically locked together and though the coil in may be made with considerable precision, these irregularities are bound to be present to some degree. Moreover, tubing itself is irregular to some degree due to the manufacturing processes. Added to the inherent variations in diameter and thickness of the tubing, is the deformation of the turns due to the winding or fabrication of coil I 0. Some flattening of the normally round conductor may occur during fabrication thereof.

The essential problem, then, is to provide a minimum of mechanical friction regardless of the irregularities above described, without loss of efi'ective and efficient electrical contact at all points. In accordance with the present invention, the elongated conductor 20 i about twice the diameter of the conductor which forms the coil Iii. As already stated, by utilizing a large central conductor, it is unnecessary to cool it because of the greater radiation of heat therefrom, and because less heat is generated in it due to its lower resistance. Moreover, the larger diameter provides a relatively stable bearing surface for the member 31. This slider 31, as best shown in Fig. 2, is provided at opposite ends thereof with a plurality oi! resilient fingers 51 and 55. Each contact finger is relatively thin at its mid-section 51a, terminating with a thickened end portion 51b. The base portion is provided with a recess 51c arranged to receive the reduced end portion 31a of the slider 31. By forming the resilient contact fingers 51 in semicylindrical array, a shown in Fig. 4, two sets may be fastened to each end of the slider 31 as by the set screws to form contact fingers which completely encircle the conductor 20.

It will be observed that the bearing surface of the slider 31 against the conductor 20 is restricted to the relatively narrow areas between the broken 50 lines extending vertically across the conductor 20 in Fig. 2. Sufllcient clearance is provided to permit a slight tilting action. Thus as the arm 35 is tilted to the left as viewed in Fig. 2, the arm 36 will be tilted or moved to the right. During such tilting action, the upper half of the resilient contact fingers I1 and the lower half of the fingers 58 will be flexed, while the remaining contact fingers will have a part of the normal bias relieved. The provision for this tilting movement 50 takes care of a number of irregularities which otherwise would introduce binding during adjustment of the arms 35 and 36 with respect to the coil II).

To take care of irregularities in the diameter of the coil II), the resilient contact heads 44 and I are carried by pistons movable within the arms 35 and 36. For example, it will be observed that the lower head 45, Fig. 2, is secured to a circular member or disc 6i! which is secured by a screw to a piston head 68 from which there extends a rod 61. The rod 81 is provided with two additional cylindrical members or pistons 68 and 69. Between the slider 31 and the cylindrical member 69, a compression spring 10 is mounted. This spring pushes against the member 69 and tends to move it outwardly of the cylindrical tube Il formed of copper. The tube II is brazed or soldered to the slider 81'. The movement of the piston, of course, is resisted by the turn of the coil ll engaged by the contact head 45. Preferably, slots may be provided in the tube H through which there may extend pins I2. These pins cooperate with the ends of the slots to prevent movement of the assembly outwardly of the tube 1| beyond a predetermined amount. This provision simplifies assembly problems.

Similarly, the contact head 44 is carried by the rod 14 to which there are secured cylindrical members or pistons 15 urged outwardly of a tube IQ of insulating material by means of a spring 11. This tube I! has a shoulder 18a which fits under a ledge provided in a supporting tube It.

The spaced annular plates or flat cylindrical members Ii, 68 and I6 form the equivalent of tubular pistons or sliders but have the advantage of reducing friction to a minimum by their narrow cross-sectional areas.

While the piston construction just described takes care of differences in diameter of the coil, provision is additionally made for other variations such as for deviation of the turns of the coil from a true helix. For example, with the tilting action previously described, the respective heads 44 and 45, a side view of one of which, the head 44, is shown in Fix. 3, must provide flexibility. As will be seen from Fig. 3, the irmer surface of the head 44 deviates from a circular configuration. The inner surface tapers from a relatively high point it to the respective ends of the head 44, thus providing for a fulcruming movement of the head 44. In other words, if a turn of the coil deviates from a true helix, the deviation tilts the arm 35 and the head 44 about the inclined or tapered surfaces extending from the high, point 80. In other words, the cross section of the interior opening through each contact head graduall increases from the mid-portion to each end thereof to provide for a fulcruming movement of each arm and its head.

These various constructional features mutually cooperate to maintain efficient and low resistance electrical connections, while at the same time, they minimize the introduction of friction. The arms 35 and 38 may be easily rotated quickly to change the number of turns or fractions thereof included in the ircuit. The driving motor may be of relatively small size. The motor 28 always responds because friction is never present in unexpected large amounts which would otherwise cause the motor to stall. The coil makes possible the tuning of a circuit under high or even full load operation.

While a preferred embodiment of the invention has been described, it will be understood that further modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A variable inductance device comprising a helically coiled conductor, a second conductor extending along the axis of said coiled conductor, slidable means mounted on said second conductor having a pair of arms extending outwardly therefrom, one of said arms completing a connection from said second conductor to said first conductor and the other of said arms being electrically divided by insulating material, each of said arms having at the outer end thereof a plurality of resilient lingers for engaging at opposite sides of said coil adjacent turns thereof, a driving arm rigidly secured to said second conductor, torque transmitting members extending from said driving arm and into driving relation with the outer portions of said first-named arms for producing rotation thereof without application of torque through said slidable means, and means for rotating said driving arm and said torque members to produce movement of said arms and of said slidable means lengthwise of said coil.

2. A high-frequency tuning coil of helical shape, a central shaft extending through said coil, arms slidably mounted on said shaft the end of each arm slidably engaging said helical coil, one of said arms including means insulating it from said central shaft, means including the other arm for completing an electrical connection between said central shaft and said coil, a driving member connected to said central shaft in axially spaced relation with one end of said coil and having elongated driving rods extending inwardly through said coil and adjacent the turns thereof, and means carried by the outer portions of said arms forming a sliding mechanical connection with said driving rods for transmission of torque to said arms with a minimum of mechanical resistance against sliding movement of said arms lengthwise of said coil and of said driving rods.

3. A variable inductance comprising a helical coil having fixed spaced turns, variable contact means for said coil comprising a rotatable longitudinally movable member arranged vvithi said coil, said member at its respective outer ends having a plurality of resilient elements engaging turns of said coil on diametrically opposite sides thereof, said member including insulating means for insulating one end thereof from said coil, a driving and carrying member extending longitudinally of said coil, means at the center of said movable member for rotatably and slidably mounting it on said carrying member, and means including anti-friction means located near the respective ends of said movable member for mechanically connecting said movable member to said driving member.

4. A variable inductance coil comprising a helically wound coil, a rotatable shaft positioned coaxially within said coil, a sliding member carried by said shaft and electrically connected thereto, said sliding member having a pair of arms extending to diametrically opposite sides of said coil, the outer end of each of said arms having resilient means engaging a turn thereof, means for rotating said arms comprising a pair of rods extending through said coil, one on one side of said arms and the other on the other side of said arms, driving members carried by said shaft member and connected to the respective ends of said rods, a pair of rollers carried by each of said arms near the outer ends thereof, with one roller on one side and the other roller on the other side of said rods to form anti-friction bearing means therebetween, whereby torque is applied through said anti-friction means to said arms near their outer ends.

5. A variable inductance device comprising a, helically coiled conductor, a second conductor extending along the axis of said first-mentioned conductor, an electrically conductive arm electrically connected with and extending radially outward from said second conductor. means supporting said arm for rotation thereof about the axis of said second conductor and for translation axially :along said second conductor, contact means onthe outer end of said arm constructed and arranged for movable contact with said coiled conductor, a driving arm rotatable about said sec- 0nd conductor and extending radially outward,

therefrom in axially spaced relation to said first arm, and a torque transmitting member extending from said driving arm and engaging said first arm intermediate the ends thereof in a manner to eflect rotation oi said first arm in response to rotation of said driving arm while permitting relative movement between said first arm and said member axially of said member, and means for effecting rotation of said driving arm.

6. The combination with a variable inductance device comprising a helical coil having the turns thereof spaced one from the other and a conductor extending along the axis of said coil, of a contact arm the respective ends of which slidably engage said conductor and a turn driving member rotatable about the axis oi said coil, 9. driving element connected to said member and extending through said coil, means carried by said contact arm for slidably engaging said element, and means for rotatin said driving member to adjust the position or said contact arm with respect to said coil.

7. Th combination with a variable inductance of said coil, a

device comprising a helical coil having the turns thereof spaced one from the other and a conductor extending along the axis of said coil, or a contact arm the respective ends of which slida-bly engage said conductor and a turn of said coil, a driving member axially spaced from said contact arm, torque transmitting means interconnecting an outer portion oi said contact arm and said member for applying torque to said arm in a direction substantially normal to the length thereof, and means for rotating said driving member to adjust the position 01' said contact member with respect to said coil.

PAUL D. ZUI'IU.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,818,316 Gebhard Aug. 11, 1931 2,324,189 Bock July 13, 1943 

